The modern communications era has brought about a tremendous expansion of wireline and wireless networks. Computer networks, television networks, and telephony networks are experiencing an unprecedented technological expansion, fueled by consumer demand. Wireless and mobile networking technologies have addressed related consumer demands, while providing more flexibility and immediacy of information transfer.
Current and future networking technologies continue to facilitate ease of information transfer and convenience to users. In order to provide easier or faster information transfer and convenience, telecommunication industry service providers are developing improvements to existing networks. For example, the universal mobile telecommunications system (UMTS) terrestrial radio access networks (UTRAN) and the GERAN (GSM/EDGE radio access network) system are currently being developed. The E-UTRAN (evolved UTRAN), which is also known as Long Term Evolution (LTE) or 3.9G, is aimed at upgrading prior technologies by improving efficiency, lowering costs, improving services, making use of new spectrum opportunities, and providing better integration with other open standards.
An advantage of the communication systems currently under development, which continues to be shared with other preceding telecommunication standards, is the fact that users are enabled to access a network employing such standards while remaining mobile. Thus, for example, users having mobile terminals (or user equipment (UE)) equipped to communicate in accordance with such standards may travel vast distances while maintaining communication with the network. By providing access to users while enabling user mobility, services may be provided to users while the users remain mobile.
A basic architecture of a communication system may include a core (e.g., a third generation (3G) core, an evolved packet core (EPC) or the like) in communication with various nodes (e.g., base stations, access points, node Bs (NBs) or evolved node Bs (eNBs)). Each of the nodes may transmit over an air interface to a particular region or regions defined as cells. The nodes may define corresponding cells in which communication coverage is provided by a respective node. As such, a geographical area may be provided with coverage defined by a plurality of cells. Moreover, given that multiple radio access networks are currently in simultaneous use, it is possible that cells of different radio access technologies (RATs) may overlap.
System Architecture Evolution (SAE) of the third generation partnership project (3 GPP) release 8 specifies a packet switched (PS) core network architecture for LTE. By definition, certain circuit switched (CS) services (e.g., voice, short message service (SMS), UDI, etc.) are not available in a PS only core network. Accordingly, CS services may only be available if a particular terminal (e.g., a UE) moves (or falls back) from the LTE/SAE domain to a CS domain of a legacy RAT (e.g., GERAN or UTRAN) whenever there is an incoming or outgoing CS service indication such as a page, CS service request or the like.
Previously, establishing a CS fallback capability has been defined as a simple procedure of triggering the terminal to move to the legacy RAT where there is CS domain support in response to a CS service indication. There have been two main RAT change methods proposed including PS handover and redirection. Redirection is a method involves E-UTRAN sending a message (e.g., a RRC CONNECTION RELEASE message) with redirection information indicating to which RAT and carrier the terminal is to move. However, it may be desirable to implement redirection in an efficient manner with respect to radio network resources.